(1) Field of the Invention:
This invention relates to a process for preparing a printed-circuit board, and more particularly to a process for preparing a printed-circuit board having through-holes therein.
(2) Description of the Prior Art:
Recently, an improved process for preparing a printed-circuit board has been developed, which process comprises subjecting a copper plated laminated, insulative plate (hereinafter may be referred to as a "plate") for use in a printed circuit and having through holes such as through-holes to electrodeposition coating in a photocurable electrodeposition coating composition bath to form a resist film on the plate, exposing the resist film to an active light through a wiring pattern mask, removing a non-exposed area of the resist film with an alkaline water or the like, etching away the exposed copper foil to form an etching resist pattern film on the plate, and removing the etching resist pattern film to prepare a desired printed circuit.
However, the aforementioned process has such a drawback that on exposing the resist film coated on the plate to the active light, an area of the resist film, in which the resist film on the plate forms a vertical surface to the active light, is exposed to the active light to form an etching resist pattern film having excellent film properties, whereas through-hole wall areas, in which the resist film forms a parallel surface to the active light, is not exposed to the active light because the active light passes through along the upper surface of the resist film, the non-exposed area is washed away with an alkaline water or the like and the copper foil, which is required for the printed circuit, is further removed by the etching treatment in the following step, resulting in making it impossible to form a conductive through-hole. Further, the aforementioned process has another drawback in that irradiation of the active light in such a dose as to be necessary for photocuring of the resist film in the abovementioned through-hole wall area results in irradiation of the active light in an excessive dose onto the resist film forming a vertical surface to the active light, in making it difficult to remove the film, and in making it impossible to form a conductive printed-circuit.